Process and device for restoring lost circulation



Jan; 9, 1968 H. K. VAN POOLLEN 3,362,476

PROCESS AND DEVICE FOR RESTORlNG LOST CIRCULATION Filed Oct. 10, 1966 Fig. 4

' INVENTOR. HENDRIK K. VAN POOLLEN wuwmpj ATTORNEY United States Patent 3,362,476 PROCESS AND DEVICE FOR RESTORING LOST CIRCULATION Hendrik K. van Poollen, Littleton, Colo., assignor to Marathon Oil Company, Findlay, Ohio, a corporation of Ohio Filed Oct. 10, 1966, Ser. No. 598,557 3 Claims. (Cl. 16621) ABSTRACT 015 THE DISCLOSURE Lost circulation encountered in drilling wells is restored by:

(a) introducing into the area of lost circulation linked,

sealed, flexible, water-soluble bags filled with circulation-restoring materials which on contact with formation fluids form an integral mass;

(b) effecting dissolution of the bags at the point of lost circulation to release the circulation-restoring materials from the bags;

(0) allowing the circulation-restoring material to react with fluid in the well-bore to form an integral mass; and

(d) drilling through the mass.

The bags can be linked and the terminal bag attached to an anchor, which is first introduced into the well-bore.

This is a continuation-in-part of my application, Ser. No. 275,997, filed Apr. 26, 1963, and now abandoned.

This invention relates to the use of linked water-soluble containers in processes for restoring lost circulation and more particularly to the use of flexible, Water-soluble materials in such operations.

Nature presents many types of lost circulation problems to the well driller. Sometimes the drilling fluid is lost through many minute fissures in the rocks being drilled. Other times, the bit will drill into underground rivers. These rivers can be swift or slow, and their beds flat or sloping. Similarly, a cavern as big as Mammoth Cave may be drilled into. Again, sloping floors may be found.

Various solutions have been proposed to overcome these difiiculties. United States Patent 3,190,373 teaches a process wherein the drilling pipe is placed a short distance above a lost circulation zone in a Well-bore and rigid three-piece casings cast from water-soluble materials are injected therein alternately with mud and water. This patent attempts to prevent the rigid casings from becoming lodged and prematurely blocking the Well-bore by using the drill pipe as an external injector means. However, serious premature blocking can still occur in the drill pipe and it may be necessary that mud or water be pumped down with the rigid casings. Attempting to inject the rigid casings Without the protection of the external injector means (drill pipe) results in greatly increased danger of premature blocking because of the numerous rough and uneven spots in the well-bore at which the rigid casings can snag and lodge across the well-bore.

If the floor of the cavern or underground river is sloped appreciably, large numbers of the rigid capsules may roll downhill and be, for practical purposes, wasted. My invention eliminates the danger of the capsules rolling down sloping floors.

Another advantage of the present invention is that it substantially eliminates the serious problem of the rigid capsules lodging in and prematurely blocking the wellbore without the need for an external introducing means.

Costly casting and threading the rigid capsules is also rendered unnecessary by the present invention.

3,362,476 Patented Jan. 9, 1968 "ice Reinserting the drill string to compress the rigid casings at the bottom of the well-bore is superfluous in light of my discovery.

The foregoing advantages can be obtained by introducing into an area of lost circulation a plurality of linked, sealed, flexible, water-soluble bags filled with particulatecirculation-restoring materials, dissolving the bags, allowing the circulation-restoring materials to react with water to form an integral mass at the point of lost-circulation and drilling through the integral mass.

Preferably, the bags are formed from tubing, as tubing can be cut into desired lengths. The tubing is sealed at one end to provide a bag, filled with cement or the like, and sealed at the other end when filled.

Some formation conditions require thicker water-soluble protective devices than do others, i.e., deep formations and hot formations which cause quick dissolution of the Water-soluble protective device. Utilizing my invention, no great inventory of bags is required as a number of bags of one size can be fitted, one inside the other, as desired and sealed to form a protective device of needed water resistance.

In tubing form, the bags can be flattened for shipment and warehoused by simply covering the roll. Furthermore, the filled, sealed bags formed from the tubing can be linked together, attached to an anchor, and introduced into the formation as a unit, thereby reducing the tendency of the tubing to roll downhill.

As above mentioned, flexible, substantially non-stretching, water-soluble bags are utilized in the process of my invention. A number of materials are suitable for the manufacture of such bags and tubing which can be cut to form bags. Polyvinyl alcohol, ethylene oxide modified polyvinyl alcohol, polyethylene oxide, dextran, gelatin and methyl cellulose are examples of materials which are suitable for the purposes of this invention.

Where tubing is utilized to form the desired bags, the ends of the tubes can be heat-sealed, clamped off with metal or plastic clamps, or glued to effect the desired closure. Combinations of these sealing means can be utilized where necessary. The bags should be substantially non-stretching when filled so that they will not be compressed longitudinally by the pumping pressure sufiiciently to cause lateral stretching and resultant binding in the well-bore.

The usual sealing compositions are utilized in the proc ess of this invention; for example, dry, neat cement and bentonite. These materials can be modified with mate rials, such as quick setting agents, Weight controlling agents, and reinforcing solids, which serve to enhance the utility of the invention.

The attached drawings more fully illustrate my invention. In the attached drawings:

FIGURE 1 is a sectional view through a filled bag;

FIGURE 2 is a fragmentary view of a Well showing linked bags descending into a formation and falling into space around an anchor;

FIGURE 3 depicts a merged blob of cement which has expanded into place within the formation; and

FIGURE 4 depicts the drill bit passing through the hardened cement.

The filled bag of FIGURE 1 shows a tube 11 which is rolled at its bottom end and which is fitted with a clamp 12 to prevent the tubing 11 from unrolling. Neat cement Within tube 11 causes bag 10 to be substantially rigid. At the upper end of bag 10, the tubing 11 is closed by a second clamp 12.

Water-soluble cord 14 is afi'lxed to bag 10 by clamp 12 and serves to connect bag 10 to a second bag or to an anchor, if necessary.

One aspect of the process of this invention is depicted in FIGURES 2, 3, and 4. In FIGURE 2, anchor 20 has been lowered into a large sloping subterranean formation 21; and bags 10, coupled together by cords 14, have piled around the anchor to fill the cavern 21 adjacent to and below the bore hole 22. As depicted, long bags are lowered into cavern 21 to form a retaining means for later, smaller bags 10 which fill the interstices between the longer bags.

As shown in FIGURE 3, the bags 10 have dissolved, and the cement 13 has formed a unitary mass 23. In FIG- URE 4, mass 23 has hardened and circulation has been restored. Drill bit 25 is shown boring its way through mass 23.

It is obvious that the bags of this invention can be used for purposes other than for restoring lost circulation in drilling operations. Thus, bags of quick-setting cements could be used in damniing operations, grouting operations, etc.

What is claimed is:

1. A method of restoring lost circulation encountered in drilling comprising:

(a) introducing into the area of lost circulation a plurality of linked, sealed, flexible, water-soluble bags filled with particulate circulation-restoring materials which react with water to form an integral mass,

(b) substantially dissolving the bags at the point of lost circulation to release the particulate circulationrestoring material,

(c) allowing the circulation-restoring material to react with formation water to form an integral mass, and

(d) drilling through the integral reacted circulationrestoring material.

2. The process of claim 1 wherein the bags are linked and a terminal bag is linked to an anchor, said anchor being introduced into the area of lost circulation prior to the introduction of the terminal bag to which the anchor is linked.

3. A plurality of linked, sealed, water-soluble bags filled with particulate material reactive with Water to form a unitary mass, said bags being substantially non-stretching and rigid when filled with said particulate reactive material.

References Cited UNITED STATES PATENTS 2,609,880 9/1952 Dyer l662l 2,634,098 4/ 1953 Armentrout 72 2,748,867 6/1956 Lissant 166-42 X 2,768,693 10/1956 Hughes 166-21 2,824,611 2/1958 Burch l66-57 3,190,373 6/1965 Weathersby l661 17 X STEPHEN J. NOVOSAD, Primary Examiner. 

